joiningofdissimilar0automotive materials - lbcg · 4/3/2015 pkm 1 joiningofdissimilar0automotive...
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4/3/2015 PKM 14/3/2015 PKM 1
Joining of Dissimilar Automotive Materials
P.K. Mallick
William E. Stirton Professor of Mechanical EngineeringDirector, Center for Lighweighting Automotive Materials and Processing
University of Michigan-DearbornDearborn, MI 48128
OutlineDissimilar Materials in Automotive Body and Chassis ApplicationsJoining OptionsMaterial Properties to Consider for Joint EvaluationJoint Evaluation MethodsAdhesive Joints
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Automotive Materials ScenarioAutomotive Body Structure/Frame and Chassis Members/ Body Panels/Seat Structure etc.Steels (Stamped/Roll Formed)Aluminum Alloys (Stamped/Cast)Magnesium Alloys (Cast)Sheet Molding Compounds (SMC) (Compression Molded)Thermoplastics and Thermoplastic Matrix Composites (Injection Molded and Compression Molded)Carbon and Glass Fiber-Epoxy Composites (RTM)
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Automotive Materials Scenario
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Mercedes-Benz CL (2004)
Current and Future MaterialsSteels Al Alloys Mg
AlloysThermo-plastics
Thermoplastic Matrix Composites
Thermoset Matrix Composites
DQ AA 5182 AZ 91 PP SFT SMCIF AA 5454 AZ 31 ABS LFT GFRPBH AA 5754 AZ 80 PA-6 GMT CFRPHSLA AA 6009 PA-66DP AA 6016 PCTRIP AA 6061 PETTWIP AA 6111 PBTBoron
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Joining Options for Metals
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Liquid Phase Welding
Solid Phase Welding
Mechanical Joining
Adhesive Joining
Resistance Spot Welding
Friction Stir Welding (FSW)
Bolting Adhesive Bonding
Gas-Metal Arc Welding etc.
Friction Stir Spot Welding (FSSW)
Screwing Weld-Bonding
Laser Welding Magnetic Pulse Welding
Self-Piercing Riveting (SPR)
Rivet-Bonding
Brazing Ultrasonic Welding Clinching
Joining Options for Plastics and Composites
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Thermoplastics and Thermoplastic Matrix Composites
Thermoset Matrix Composites
Vibration Welding Mechanical FasteningUltrasonic Welding Adhesive BondingResistance Welding Hybrid (Mechanical + Adhesive)Mechanical FasteningAdhesive Bonding
Joining Options Between Dissimilar Materials
Material Combination
Joining Options
Steel and Al Alloys Arc Welding (Cold Metal Transfer, Transition Inserts),FSW, SPR, Clinching, Adhesive Bonding
Steel and Mg Alloys SPR, Bolting, Adhesive BondingAl and Mg Alloys SPR, Bolting, Adhesive BondingSteel and CFRP Adhesive Bonding, Bolting, Hybrid Joining
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Friction Stir Spot Welding of Aluminum and Polypropylene (Research at the University of Michigan-Dearborn)
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TOP VIEW
BOTTOM VIEW
Average Failure Loads for all Joint Configurations
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Type of Joint
Ave
rage
Fai
lure
Loa
d (k
N)
Highest Average Failureload for Adhesive JointsLowest Average Failureloads for Adhesive JointsHighest Average Failureload for Friction JointsLowest Average failureLoads for Friction Joints
Adhesive joints Friction joints
Material Properties ConsiderationMechanical Strength (Yield or Tensile)Elastic ModulusFormability (n and r)
Thermal Coefficient of Thermal ExpansionThermal ConductivityMelting Temperature
CompatibilityMetallurgical compatibility (Solubility, Chemical Reactivity, Wettability, etc.)Electrochemical compatibility
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Mechanical Properties
Material Density(g/cm3)
Modulus (GPa)
YieldStrength (MPa)
Tensile Strength (MPa)
%Elongation
DQ Steel 7.87 207 185 320 42DP Steel 7.87 207 400 700 19-25Boron Steel 7.87 207 1100 1500 5-7AA-5182-0 2.7 70 130 275 24AA-6011-T6 2.7 70 275 310 12MA-AZ31-H24 1.74 45 220 290 15MA-AZ91D 1.74 45 150 230 3CFRP (0/90/ 45) 1.55 45.5 ---- 580 1.5
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Thermal and Electrical Properties
Material Coeff. of Thermal Expansion(10-6/oC)
Thermal Conductivity(W/m.oK)
ElectricalResistivity( -cm)
SpecificHeat (J/g.oK)
MeltingRange(oC)
Steels 11-12 52 16 0.5 1500
Al Alloys 22-24 150-200 3.5 0.9 660
Mg Alloys 26 70-100 9-17 1 650
Polymers 60-200 0.1-0.5 1018 700-2000 130-300
CFRP 0-0.9 10-20 --- --- ---
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Corrosion
Material Corrosion Potential (V)
Environmental Consideration
Iron -0.440Aluminum -1.662 Formation of Surface Layer Magnesium -2.363 Formation of Surface LayerPolymers --- Temperature, Humidity, Auto FluidsCFRP --- Temperature, Humidity, Auto Fluids
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Joints of Dissimilar MaterialsDifferences in modulus, yield strength and strain hardening characteristicsHigh stresses at the interface between dissimilar materialsStress concentration at the interface corners and corner cracksUnwanted springback, especially in tailor-welded blanks (due to difference in yield strength to modulus ratio)
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Joints of Dissimilar Materials
Difference in coefficients of thermal
Detrimental residual stresses after the joining operation and/or thermal stresses during the service periodDistortion and dimensional problemsMicrocracks and microvoids
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Joining of Dissimilar MaterialsJoining with composite materials must
Are anisotropicDo not show yieldingHave different failure modes (debonding, delamination, etc.)May not formableAre not weldableHave different surface characteristics than metals
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General Considerations for Joint Development Material combination (Difference in material characteristics)Performance requirementsMaterial thicknessJoint design (type, overlap, distance between joints, joint pattern, etc.)Thermal expansionPotential for corrosion and environmental degradationNeed for mechanical fixtures and constraints
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Considerations for Liquid Phase WeldingPre-joining surface condition and surface treatmentsDifference in melting temperaturesHeating and cooling rate effects on the microstructureFormation of brittle intermetallic compounds during joiningPost-joining stress-relief treatments
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Evaluation of Joints
Strength Durability Degradation Other
Lap ShearT-Peel
FatigueCrashCreep
GalvanicCorrosionEnvironmental Degradation
Phase DiagramFailure ModesMicrostructureFracture Toughness
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Static Test MethodsLap Shear Test T-Peel Test
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Fatigue Test MethodsShear Fatigue
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Fatigue Test MethodsTension Fatigue
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Corrosion Test MethodsBase Materials and Joined MaterialsLaboratory Tests for Basic Corrosion Behavior in Automotive EnvironmentWeight Loss in Immersion Tests, Polarization TestsEffect of Corrosion on Mechanical Properties
Accelerated Cyclic Corrosion Tests in Salt SolutionSalt Spray TestsIn-Vehicle Tests
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Adhesive JoiningWith increasing use of dissimilar materials, adhesive joining is becoming more accepted.Numerous advantages:More uniform stress distributionIncreases structural stiffness Little or no alteration of the substrate propertiesLess dependent on the materials to be joinedRelatively easy to adopt on the production line
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Considerations for Adhesive Joining
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Adhesive selection issue Adhesive propertiesSurface preparation issuesJoint design issuesQuality control issues (including NDT)Environmental degradationLong term durability Creep, Fatigue
Adhesive PropertiesShear modulus, shear strength, shear strain-to-failureStress-strain properties (needed for FEM) at RT, low and high temperaturesCoefficient of thermal expansionFracture toughness (Resistance to crack propagation determined by DCB test)Creep (long-term)Effect of environment (moisture, elevated temperature, freezing temperatures, salt, etc.) both short term and long termAdhesion properties (e.g., surface energy)Chemical resistanceViscosity
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Adhesive Selection Adhesive selection depends onPerformance requirementsSurfaces to be bondedAdhesive curing or bonding timeExpected service environment (temperature, humidity, etc.Adhesive application methodCost
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Adhesive Joint EvaluationStatic Tests, such as Lap Shear, T-Peel, WedgeFatigue TestsDynamic Tests (Impact, Vibration)Creep TestsEnvironmental Tests (Elevated Temperatures, Freezing Temperatures, Salt Solution, etc.)
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ConlusionsJoining of dissimilar materials is one of the key challenges in a multi-material automotive structure.Evaluation of dissimilar joints should not only include a variety of short-term and long-term tests, but also analytical tools, such as FEM with realistic material properties.
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Thank you.